Gamma-caprolactone is commercially and industrially attractive because of its use as a flavor additive in foods and tobacco and for its potential as an intermediate for insecticides.
Gamma-caprolactone (.gamma.-caprolactone) has the structure: ##STR1## Gamma-caprolactone is also known as 4-hexalactone and 4-ethyl butyrolactone and in Chemical Abstracts, it is identified as 5-Ethyldihydro-2 (3H) furanone with a registry number of 695-06-7.
Various prior art methods exist for the production of gamma-caprolactone, but these methods are either expensive or do not produce good yields.
For example, U.S. Pat. No. 3,935,235 to Hardy, et al. discloses a multi-step process for the production of gamma-caprolactone. According to the process of Hardy, et al., a feed-material containing the group --O--(CR.sub.2).sub.n --CO-- in which R represents a hydrogen atom or a methyl-group and n is an integer from 5 to 11 in a macrocyclic ring or an acyclic chain, is heated to temperatures of from 300.degree. to 500.degree. C. to form a mono unsaturated acyclic carboxylic acid. The mono unsaturated acyclic carboxylic acid is separated and subjected to cyclising by contacting it with a catalyst comprising a strong protonating agent such as sulfuric acid, toluenesulphonic acid, formic acid, oxalic acid, trifluoroacetic acid, a cation exchange resin in the free-acid form, a strongly acidic mixture containing hydrogen ions such as hydrogen halides in acetic acid or similar strong protonating agents.
The Hardy, et al. process disadvantageously requires a two-step reaction as well as an intermediate separation step to produce gamma-caprolactone. Further, the Hardy, et al. process requires high temperatures (at least 300.degree. C.) to perform the first step of its process.